Lead refining apparatus



A. E. HALL LEAD .REFINING APPARATUS s sheets-sheet 1 Filed NOV. 8, 1929www@ Jan. 12, 1932. A. E. HALL v LEAD REFINING APPARATps Filed Nov. 8.1929 3 Sheets-Sheet 2 Jan. l2, 1932. A. E. HALL 1,840,946

LEAD REFINING APPARATUS Filed Nov. 8, 1929 3 Sheets-Sheet 5 .A50crystalsweretransferred Parental Jn. 12, 1932 y PATENT OFFICE LRTHUB E.HVAIL, OF PERTH AMBOY, NEW J' EBSEY 'LEAD REFINE@ APPTUS Applicationfiled November 1929. Serial No. 405,5?8.

This invention relates to lead reining and is more particularly directedto a process and pparatus ier the removal of bismuth from sad.

The metal bismuth is found as an impurity in lead and whenpresent ineven small quantities, say upwardsof 6.15%, renders the leadunsatistaetorn to a large portion of the lead consumers. able sheathing,lead pipe, sheet lead, battery plate grids and lead for paint makingpurposes and, other purposes will not tolerate lead containing evensmall quantities such as 0.15%. If the bismuth content is reduced to0.034% or less the lead produced i5 is satisfactory to the trade. At thepresent time it is possible to produce lead containing such low quantiesof bismuth by the electrolytic process of refining, and by segregatingores, but the electrolytic process is an expenzo sive one and itsexpense increases as the quantity of bismuth in the lead increases.Where Y lead bismuth contains less than approximately 97% lead it hasbeen Jound advisable to apply both a re process and later an electro-2.5 lytic process on the same lead with the combined cost of a littleless than le per pound for such treatments. Y

In 1900 Stephen Tredinnick who had been wor 0 at a plant in Nevada wherethe separationof silver from lead was being practiced, was granted a U.S. Patent No. 662,836 for an apparatus for refining and desilverizinglead, and somewhat later it was attempted to employ the apparatusdescribed in his patent for the removal of bismuthY from ead and theconcentration of the bismuth .in a relatively small amount of lead. Theapparatus involved' included a. 'number of kettles which were separatelyheated and agitated in 40 an attempt to insure uniform heatingthroughout by blowing steam into the kettles.

Ater heating up of a charge in one kettle, 1t was allowed to crystallizein part and the kettle was then lifted by a hydraulic ram and the moltencontents were allowed to flow into a second and adjacent kettle, afterwhich the remaining crystals were melted in the first kettle and then,this kettle still bein elevated by means of the hydraulic ram, 't emelted by gravity to a third vand adjacent kettle. Theprocess was not acontinuous one andV involved a large percentage of idle equipmentcontaining metallic lead whose processing was awaiting the release ofother apparatus in the refining group. The apparatus also presentedconsderable other diiiculties in operation which resulted in arelatively small output and an exorbitant cost along with poisonin ofthe operatives due to the production of ne particles of dross blown up bthe steamused in agitation of the kettles. .'Illiese disadvantagesresulted in abandonment of the Tredinmck apparatus for the purposementioned and since then it has l,been necessar to rely on the costlyand laborious electro ytic process.

The principal object of this invention accordingly is to provide asimple, inexpensive, and eflicientv apparatus for refining lead to lowerits bismuth content which shall do away with vthe disadvantages of theelectrolytic process and practice mentioned under the Tredinnick patent.Another object of the invention is to provide a simple eiiicient.apparatus which shall permit a continuous separation of bismuth fromlead, which shall avoid holding large masses of lead idle while waitingfor available a paratus for processing, which shall permit a simpleeffective control to`be maintained for the production of lead containingdesired percentages of bismuth and in accordance with the bismuth conjtent of the raw material as received. Other objects will be in partobviousl and in part pointed out hereinafter.

' The invention accordingly comprises the 'novel vapparatus andcombinations thereof, speciicjembodiments of which are described hereinby way of example only and in accordance with the manner in which I nowprefer to ractice the invention.

urther and 'more specific objects, features and advantages will clearlyappear from the detailed description given below taken in connectionwith the accompanyin drawings which form a part of this speci catibn andillustrate by way of example one embodiment of the invention.

In the drawings, Fig. 1 is a diagrammatic plan view of a preferredembodiment of my by continuously rotating screws and partially.

and alaunderLlserv' a heated kettle on the right;

Fig. 4 is a diagrammatic end elevation of the series of crystallizersand kettles;`

Fig. 5 is a sectional plan view of a part of the series ofcrystallizersand kettles taken on the line 5 5 of Fig. 3, certain parts being omittedfor the sake of clearness; and

Fig. 6 is a sectional elevationtaken on the line 6-6 of Fig. 5,

Referring now to the drawings, and particularly to Figs. 1 and 2, I havedesignated a series of crystallizers or baths there shown r as C1 to C13inclusivecandthe kettles corresponding thereto and into which eachcrystallizer or bath delivers to K1 to K13 respectively and inclusive.These crystallizers and kettle units constitute a series at one end ofwhich, namely at K1, lead of the lowest bismuth -content produced isobtained and at the opposite end of the series lead with the highestbismuth tcontent is obtained.

These crystallizer-kettle units, C1, K1, C2, K2, C3, K3 and so on arepositioned so as to maintain therethrough a continuous and unobstructedavity flow of leadbismuth in which the ismuth is increasing and anopposite flow which is partially by gravity of lead-bismuthwith-increasing content of lead. To accomplish the gravity ilow, each c'stallizer, for example C1, is set at a he1ght,preferably 6 inches abovethe next c stallizer C2 inthe series. In accordance wlth thisarrangement, the

' metal level of C2 is at a height of 6 inches higher than the metallevel of C3, and the metal level of C3 isv at a hei ht of 6 inches ihigher than thexnetal levelo C4, and so on through the series. Betweeneach crystal-l lizer or bath is asubstantially horizontal o n launderserving to convey molten leaid-y is-l muth alloy from one crystallizeror bath to the next -b gravity due to the head existing between ecrystallizers, thus between C1 and C2 is a launder L1, between C2 and C3-is a launder L2 and 4so on throughout the series of launders L8 to L12occur, L12 being positioned'between crystallizer C12 'and C13 as an exitfor-the lead containing higher bismuth. Y

'The ow of lead-bismuth alloy in which themnount of lead is increasingis maintained The crystallizers or baths are maintained at a suitabletemperature to keep a'molten mass of combined lead and bismuth withcrystals of lead-bismuth, which crystals will naturally:

contain less bismuth than the bismuth content of the molten mass, andcorrespondingly more A lead; The proportion of vlead-bismuth crystals tomolten metal in the baths will be-maintained at a ratio which will giveldesired results'. I find 57% crystals and 43% molten metal maintainsproper grades in the case` where the raw. material containing 0.164%bismuth is charged into K6 when-a product from K1 is desired containing`0.034% bismu'th, but other grades of raw material and other desiredgrades of products may indicate other proportions. v

The crystals are moved out of the crystallizer or bath by thev rotatingscrews, each screw delivering into its corresponding kettle at apre-determined rate depending upon the l area of the screw and of courseupon the proportion of crystals to molten metal present as determined bythe temperature` maintained. In each kettle the crystals received aremelted by an oil burner or other source of heat and in melted conditionare allowed to'flow by gravity throu h a series of open ducts orlaunders` D1 to 12 inclusive. The duct leadin from the kettle K2. tocrystallizer C1 is esignated as D1, from the kettle K3 to C2isdesignated as D2 and so on to the end of the series. from the kettleK1 and is an outletvfor the lead containing the lowest content ofbismuth. The launders L1 to L12 inclusive 1 of concrete or othersuitable material. The bottom 2 of the crystallizer is inclined at anangle of about 90 tothe lower end wall 3 ofy rIhe duct D13 leads l-material such as cast iron mounted-.in a base the crystallizer and thebottom wall is set at about an angle of 40 to the horizontal beingheldin position by the concrete base 1. Mounted in suitable bearings onthe end walls is a rotatable shaft 4y which is'rotatedby an outsidesource'bf power .not shown,

and is in the form of a helix being perforated throughout with drawingholes about fg inches, preferably, in diameter. The bath of lead-bismuth6 contains approximately the ratio 57% crystals to 43% molten mass-andthe screw 6 as it rotates moves these crystals out of the molten bath,draining-back any Y molten material through the perforations 5,

the crystals being deposited in the kettle K6. The kettle K6 is mountedon suitable pillars of refractory material 7 and is surrounded by arefractory lire wall 8 through which an oil burner 9 for supplying heatto the kettle K6 is provided. The crystals passing into theV burner 9.

The arrangement for heating the upper portion of the crystallixzersdsshown in Figs.

. 5 and 6. The description of one heating means for a crystallizer willsufiicefor all as the heating means is preferably identical throughout.As shown in Figs. 5 and 6, the gases passing from the burner 9 passunder the kettle K6 and up through two ducts 10 and 11 at the end of thekettle on either side of the .crystallizen These ducts are controlled byhand-operated dampers 12 and 13 to allow part or all of the gas to passupwardly without passing around the crystallizer C6 or else part orsubstantially all of the burner gases may pass along the side walls ofthe crystallizer in order to heat that part ofthe crystallizer above thelevel of the lead therein. For this purpose openings 14 and'15 areprovided respectively in the ducts 10 and 11 at a oint between the leadlevel in crystallizer 6 and the top of the crystallizer tank. This ductleads respectively into flues 16 and 17, each of which is 'shaped tofollow the outline of the crystallizer wall above the lead level. At theend of the crystallizer away from the ducts 10 and 11 the flues 16 and17 are Hattened out as shown in Fig. 5 joining one another to make'aflattened iue 18 which communicates by a branch 19 with a common pipe 20leading to the stack 21. Gases from flues 10 and 11 after passingtherethrough may also be led to the stack 21 by connections not shown.Dampers. 12 and 13 are provided with handles so that they may be movedin the ducts 10 and 1l and positioned to cause all of the gases to passup the conduits 10 and 11 when it is not desired to heat the upper partof the cry stallizers or to divert part or all of the gasesalong'tie ues16 and 17 te sired.

Each of the iiues 16 and 17 has a crystallizer wall forming one verticalside of it in each case, the other walls of the 4fiuesas well as thewalls of the ducts being made of suitable refractory material. Theseheated iiues serve thepurpose of preventing solid chills on the innerside of the wall above the molten metal level thereof. Such chills areto be avoided because they not only impede the rotary movement of thescrews but cause a solid lead bismuth compound to form which may bedifferent from the constitution of the crystals in the crystallizers.

Each of the screw conveyors S1 to S13 is driven in a manner similar tothat shown with the screw conveyor S6 in Fig. 3. A common shaft 22drives the( various screw conveyors. A'tooth pulley 23 is mountedopposite eachcrystallizer tank communicating through a chain 24 withtooth pulley 25 mounted to drive a worm 27 mounted on the crystallizerand driving a worm wheel 28.. The latterv is mounted on the end of theshaft 4 of the screw conveyor S6. I preferably maintain the revolutionsper kminutejofxall screw conveyors the same. Once started the speed ofthese conve ors need not be adjusted. [he rate of crystal elivery intothe ketties is controlled as heretofore Vpointed out by the temperaturemaintained in the crystallizers and hence the quantity of crystalsproduced. This temperature is adjusted by means of the oil burnersunderneath the various kettles and control of the plant by control ofthe heat supplied to these burners so that a greater or less tonnage tobe produced at the endsV of the series -is secured.

The typical crystallizerand kettle shown in Fig. 3 1s repeated in eachof the other crystallizers and kettles represented inthe group C1 to C13inclusive and K1 to K13 inclusive, including the inclination of thecrystallizer, the form of the conveyor, positioning of the kettle andthe oil burner, ducts and iiues for adjusting the temperature thereof.

As shown particularly in Figs. 1 and 2, the respective diameters andareas of the kettles, crystallizers and screws varies, the larger onesbeing on the left andA being graduated to the smallest on the right ofthe series.

This graduation is arranged proportionately to the amount of work doneby each unit,

The overflow levels for the various crystallizers for crystals 'beingmoved into the respective kettles are designated respectively as' O1 toO13 inclusive, see particularly Y Fig. 4.

In carrying out the process of separating lead from bismuth, leadcontaining bismuthv in the proportion of .164% as an example, isavailable as astarting material and is employed in the process althoughit will beunderstood thatv lead with higher or lower bismuth contentsmay be employed to commence the process. Thls material is melted andcharged into the crystallizer C6 where it attains a temperature suchthat` the mass will contain approximately 57% of lead-bismuth withcrystals and about 43% of molten material approximately 317 to 327 C.The screw conveyors S1 to S13 are started to rotate and the oil burnersfor kettles K1 to K13 are started to bring the temperatures in thesevarious kettles up to the proper points, all of the crystallizers havingbeen brought to and being maintained at a suitable temperature forproviding the desired ratio of crystals to molten .material therein .asreceived. The crystals.A are continuously transferred from thecrystallizer into the melting kettle K6 which is now at a suitabletemperature to melt the crystals whereupon they flow through D5 intocrystallizer C5 which is at a suitable temperature to maintain the ratioof crystal to molten-condition of 57% to 43% or any desired ratio. Thescrew conveyor there removes these crystals as they form and moves theminto the kettle K5 where they vare melted.` The molten material in C5due to theposition of C5 above C6 tends to iow and in part flows throughL5 back into C6 where it joins molten material already there.

C6 is maintained by the molten metal flowingr from K7'and also by theheated-gases from the combustion chamber of K6 at a' slightly 'lowertemperature than C5 Where temperature is'maintained by iniiowing moltenmetal 'from K6 and also by re j lated diversion of heated gases from comustion chamber -of K5 so that from the molten material flowing from C5to C6 through L5 some crystals form and these join crystals forming frommolten material already present in C6 and these combined crystals aremoved as indicated'by S6 into the kettle K6. C6 is supplied, of course,it will be understood by fresh lots of theraw material containingbismuth of approximately 164%. The molten material in C6 will tend toflow from it to C7 due to the height of C6 above C7.r C7 ismaintained atslightlower temperature than C6 and crystals therein, these crystalsbeing removed from S7 into K7. In K7 a similar process.

to that occurring in K6 results and K7' being. 6 inches higherthanC6.the melted crystals flow back into C6. The molten material in C7passes through- L7 into C8. The

Vcrystals of lead-bismuth containing a higher content of lead `are thoseflowing by combined screw action and avity in a direction towards K1from which the material kettles. In this case it is shownas connectedtoK6 (see Fig. 1) and is intended to su ply as there connected, leadcontaining pre erably a bismuth content of about 0.164%.` If lead with alower bismuth content were su plied this tank could be connected to kette K4, K3, or if lead with a higher bismuth content were supplied thetank could be connected to K7, K8, etc. Tank T is connected to kettle K6by means of a pipe in which is connected a centrifugal pump which isintended to continuously feed the molten raw material at a temperatureslightly above its melting point into the crystallizer. Asshown on Fig.1, the successive degrees of the average bismuth content of the whole main each crystallizer or bath from C13 to C1 are 1.46%, 1.00%,

'l` he molten material is flowing entirely by gravity as I prefer fromC1 to C2,`from C2 to C3 and so on through the series, C1 to C13 havingsuccessive degrees in bismuth content of .05% to. 2.00% in the samestages just mentioned but in the reverse direction.

On the other hand the molten material is flowing entirely by gravity asI prefer, through the series K13 to C12, K12 to C11, and so on from K13to K1 to final product issuing from K1 of a grade lof 0.034% bismuth,according to the stages first mentioned.

The crystals `collected in K1 therefore will4 have a bismuth -content ofapproximately 0.034% or less and a lead content of approxlmately 99.9%

On the other hand the molten material containing the higher contents oflbismuth is Sflowing entirel by gravity, as I prefer, through theserlesof kettles from K1 to K13 with a bismuth content increasing from 042% to1.460% bismuth, according to the stages just mentioned, in the reversedirection. l

shown and describedin the specification the production of a leadcontainin 2.00% of bismuth, the content of bismuth 1n the productpassing from C13 may range to higher percentages of bismuth towards thatalloy of leadand bismuth which has the lowest melt- It will beunderstood that although I havev 'zov ing point and contains a higherpercentage of4 bismuth.

The'apparatus and process mentioned are 4simple and eicient. The rate offlow is all controlled automatically, there are no troublesome valves toget out of order uiring manual manipulation, the only contro beingexercised `by proper regulation of the tempera-ture provided by the oilburners, which "in turn controls the relative percentage of crystals andliquid in the crystallizers and hence the delivery of crystals from thecrystalhzers to the kettles. The sepation of crystals from.moltenmaterial by the rfcrated screw conveyors is` clean and e ective and themelting of the crystals introduced into the kettles is eilicientlyperformed because a relatively small mass of unmelted material isdropped into a large mass of molten material. Theprovision of a V6 inchhead of molten metal throughout the system insures that no greatpressure of this material will be exerted on theV connectionsbetween thevarious pieces of apparatus so that a long` life is assured to them andto -the apparatus. In case it is necessary to make replacements,however, these may be made promptly and inexpensively. In additioncapital outlay for the building of such a plant is relatively small. Theapparatus is so arranged in addition that there is no violent agitationor large exposure of molten metal surface and hence a minimum' oxidationof lead occurs with minimum presence of fume and danger opoisoning ofthe operatives is thus avoided. Y

rIhe process is continuous and eliminates delay in the units. There. isno mass o molten material waiting for a kettle or crystallizer to befree before it can be'processed. After the temperatures have beenadjusted throughout the units the process canbe operated without changeof temperature in the units as long as the raw material being suppliedis ot approximately the same bismuth content and it is desired toproduce a lead of approximately the same lowered bismuth content. Oneadvantage resulting from the maintenance of a uniorm temperature is thatit is not necessary to cool down or heat up large masses of refractorymaterial which are naturally poor conductors radiators and absorbers ofheat. The process is applicable of course to lead materials with varyingbis' muth contents and `in accordance with thetemperature control, thepoundage or tonnage, issuing from either the low bismuth end or the highbismuth end may be adjusted. The desired fiow of metal, namelyleadconcentrate in one direction and bismuth concentrate in the oppositedirection is automatically obtained by reason of the established levelsof the crystallizers and kettles and iiow in any other direction isprevented.

, While I have described my invention in considerable detail and withrespect to a pre- 'ferred form thereof.v I do not desire to be limitedto such details or forni-since many changes and modifications may bemade and the invention embodied in widely diierent forms withoutdeparting from the spirit and scope thereof .in its broader aspects.Therefore, I desire to cover all modifications and bination, a kettleand a crystallizer, autoy matic means for continuously moving crystalsout of the crystallizer into the kettle,l

means for melting said crystals in the kettle and delivering them inmolten condition outside of said kettle, and means to conductl moltenmaterial away from the crystallizer.

2. In apparatus for refining lead, in combination, a crystallizer-kettleunit having a kettle and crystallizer, means for moving crystals out ofthe crystallizer into the kettle, means for melting said crystals in thekettle and delivering them in molten condition to anothercrystallizer-kettle unit, and means to conduct the molten material awayfrom the crystallizer to a third unit. l

3. In apparatus for refining lead in combination, a crystallizer-kettleunit having a kettle and crystallizer, means for moving crystals out ofthe crystallizer into the kettle, means for melting said crystals in thekettle and delivering them in molten condition to the crystallizer ofanother erystallizer-kettle unit and means to conduct molten materialaway from the rst mentioned crystallizerv to the crystallizer of a thirdcrystallizer-kettle' unit.

4. In apparatus for refining lead, in com' bination, a series ofcrystallizer-kettle'units arranged in a sequence to provide anunobstructed 'gravity flow of molten] l'ead containing an increasingamount of impurities such as bismuth in one direction, and providing avflow of lead containing decreasing amounts of impurities such asbismuth in an opposite direction, each unit having a kettle and acrystallizer, means for moving crystals out of the crystallizer into thekettle, means for melting said crystals in the kettle and deliveringthem in molten condition outside of said unit, and means to conductmolten material away lfrom the crystallizer.

5. In apparatus for refining lead, in com-A bination, a series ofcrystallizer-kettle units arranged in a'se uence to provide anunobstructed gravity ow of molten lead containing impurities such asbismuth in one direction, and providing a flow of lead containingdecreasing amounts o? impurlties such as bismuth in an oppositedirection, each unit having a kettle and a crystallizer, a. conveyor ineach crystallizer for conveying crystals out of it into the kettle, aheater for melting crystals in the kettle, a duct connecting said kettlewith the next crystallizer on one side of the series and beingpositioned to allow a gravity flow of molten material from the kettle tosaid other crystallizer and a duct for conducting molten material awayfrom the crystallizer to the next lcrystallizer on the other side of theseries.

6. In apparatus for reininglead, in combination, a series ofcrystallizer-kettle units arranged in a sequgnce to provide anunobstructed 'gravity ilow of molten lead containing an increasingamount of impurities'such as bismuth in one direction; and providing afiow of lead containing'decreasing amounts of impurities such as bismuthyin an opposite direction, each unit having a kettle, a crystallizer anda conveyor for moving c stals out kettle to the crystallizer of the uniton one creasing impurit cual moving "'10.'A'crystal1izer side fordelivering melted crystals by gravity from the kettle to saidcrystallizer, and a,

launder leading from the last mentioned crystallizer to the firstmentioned crystallizer for delivering molten lead containing inby avity,to the first mentioned crysta zer, tile crystallizer-kettle unit on theother side having a duct leading from its kettle to the first mentionedcrystallizer and deliverin melted crystals containing increasing lcontent by lgravity to the crystallizer, and a launder lea ing from thefirst mentioned crystallizer to the crystallizer of the last mentionedunit to deliver molten lead containing increasing impurity by gravity.to the crystallizer of the last mentioned unit, the crystallizer-kettleunits at either end being connectedin a-similar manner te that describedon the other units but being connected to deliver, respectively, outsidethe series-for molding or otherwise, material of the highest leadcontent andmaterial of the lowest lead content. A

7. In apparatus for refining lead, in combination, a series ofcrystallizers and kettles` arranged in a sequence to provide a flow ofmolten lead containing an increasing amount of impurities such asbismuth in onedirection and providing a flow of lead containingdecreasin amounts of bismuth in an opposite direction, each crystallizerhavinga conveyor-for moving crystals out of the crystallizer intotliekettle, connections between the kettles and crystallizers inthe series,the dimensions of the crystallizers, kettles and conveyors beingproportioned to the amounts of material to be handled b each. v n8..',In'apparatus for m ing lead, in combination, a vessel for holdingmolten lead crystalsand a device for continuy crystals out of the leadwhile leaving the molten material behind.A

9. In apparatus for refining lead, in combination, a vessel for holdingmolten lead containing crystals anida: clililve or for crystals'outo eeaw'eeaving the molten matei-'La behind.

ining1 having in combination, a crystallizing f 'w into a'kettle and adevice for moving :fromthecryst'allizingtrough inw am kes. 11.A-crystalliaer-kettle unit for leadrenin having in combination' acrystallizing trough feeding im s -kaisnnd a 'rotating screw conveyorfor moving crystals vfrom the Atro'ughinto the kettle. 12. A ,iinitforlead reinto t e lin' having'in combination, a

Iscrew conveyor, having holes ierced therein for allowing molten lead torain from lead crvstals, for moving crystals from the crystallizingtrough into the kettle.

13. A crystallizer-kettle unit. for lead reiining having in combination,a crystallizing trough feedin into a kettle and a device for movin crsta s from the crystallizing trough ettle, and a heater for meltingcrystals delivered to the'kettle.

14. A crystallizer-kettle unit for lead refining having in combination,a crystallizing trough feeding into a kettle and a rotating screwconveyor for movingcrystals from-the crystallizing trough into thekettle, and a heater for melting crystals delivered to the kettle. Y

15. A crystallizer-kettle unit for lead ref ining having in combination,a crystallizing trough feeding into a kettle and a rotating screw,havingholes pierced therein for allowing molten lead to drain from leadcrystals, for moving crystals from the crystallizing trough into thekettle, the crystallizing l trough and screw being set at an angle tothe horizontal whereby the cr stals are moved upwardly out of thesolution on an incline and de osited in the kettle.

16. crystallizer-kettle unit for lead refining having in combination, acrystallizing trough feeding into a kettle and a rotating screwconveyor, having holes pierced therein for allowing molten lead to drainfrom lead crystals, for moving crystals from the crysta lizing troughinto the kettle, the crystallizing trough and screw being set at an anlgle4to the horizontal whereby the crystals are lmoved upwardly out ofthe solution on an inclineand deposited in the kettle, a heaterdelivering products of combustion to said kettle for melting crystalsdeposited therein,

Y and ducts positioned on the walls of said crystallizer above the levelof the lead bath therein for conveying said products of combustion pastsaid crystallizery to su lply heat ,to'the portions thereof situated ave said bath. In testimony whereof I have signed my name to thisspecification.

. ARTHUR E. HALL.

kettle unit `for lead reies

